Davis Enterprise Article

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Scott Crosbie often spent mornings counting yellow-billed magpies with their long tails, strips of blue feathers and noisy calls of chaw-chaw-chaw.

Then, West Nile virus hit.

In September, Crosbie began going back to roost sites in Sacramento. These were groups of trees where he'd typically found more than a thousand birds, in 2003 and 2004, while finishing his master's thesis in conservation biology at Sacramento State University.

But when Crosbie returned to two roost sites in Fair Oaks — places where neighbors remember the raucous birds gathering for years — the trees stood empty.

"I was shocked," Crosbie said. "I expected to find fewer birds, but I didn't expect to find none."

At a third roost site, in the Arcade neighborhood in northeast Sacramento, the number of birds had dropped by 22 percent.

Crosbie shared his research at UC Davis on Thursday during a daylong meeting of about two dozen experts on the yellow-bills, bird monitoring, mosquitoes and West Nile virus from academia, state agencies and nonprofit organizations.

The consensus: The mosquito-borne disease is a significant threat to the survival of the species.

Because of that, immediate research is needed on the biology and population of the birds, areas where basic information is lacking, said meeting organizer Holly Ernest, a UCD veterinarian and expert in wildlife populations and genetics.

Yellow-billed magpies, common in and around Davis, are sometimes called the Central Valley's signature bird.

Their range is limited almost entirely to the Sacramento and San Joaquin valleys and valleys in the Coast Ranges, making them one of just two birds (the island scrub jay is the other) that live only in California.

The yellow-bills are also unique because, with their black-billed cousins, they are the continent's only black-and-white land birds and one of just a few species with tails longer than their bodies.

Like others in the crow family, for reasons scientist don't yet understand, they're also particularly susceptible to West Nile virus.

The virus can cause inflammation of brain tissues, encephalitis, and meningitis, swelling of the tissue enclosing the brain and spinal cord. It is spread between birds and, on occasion, to other species, including humans, through the bite of an infected mosquito.

According to the California Department of Health Services, callers to its hot line this year have reported finding 6,596 yellow-bills dead. Of the 439 were tested for West Nile, 82 percent were found to have died from West Nile.

In 2004, 2,037 yellow-bills were reported dead. Eighty-one percent of 374 tests came back positive.

But Ernest noted that the number of birds reported may represent just a fraction of those actually felled by infection.

She cites a study that found the public noticed only 17 percent of crow decoys placed in urban areas. In rural settings, people discovered just 3 percent.

Researchers are unsure of how great the threat is to yellow-bills, in part because no one knows just how many of them there are to begin with.

The California Department of Fish and Game has placed their population at 100,000 to 200,000; another study settled on the figure 180,000.

Ernest said that both were little more than best guesses.

"Without that number, we don't know how many are being affected," she said.

Smart, elusive

Because the birds are very social, spending much of their time in groups, they're not always easy to count.

Like crows, magpies are also smart — which makes them tough to capture for banding or blood draws.

Ernest said the group dynamics of magpies aren't yet understood, either, though its importance seems clear. When what were apparently key members were poisoned in the 1980s, a coastal colony that had existed for at least 50 years rapidly declined.

The magpies' limited range means that if the virus hits hard in one area, there may not be sufficient numbers elsewhere to replace them.

But Dale Steele, senior biologist and program manager for Fish and Game's Species Conservation and Recovery Program, noted the bulk of the research done about the birds has been done in and around urban areas.

Perhaps, he said, birds living in rural areas can be a sort of reservoir for the species, allowing them to repopulate hard-hit places.

Studies on crows indicate, however, that repopulation is, at best, a slow process.

Because of this, Steele said, it will be important to learn how much interaction there is between groups of the magpies.

Another question that Ernest and her team at the UCD Veterinary Genetics Laboratory is examining: whether West Nile has caused a loss in genetic diversity in magpie populations. Such a loss could make the species less able to cope with environmental changes, including diseases.

Other habits of the yellow-bill further complicate matters: Crosbie, now working for an environmental consulting firm in Sacramento, found that magpies in urban areas often roost in trees near small streams — prime habitat for mosquitoes.

What's ahead?

In this area, the worst may be yet to come for the magpies.

Mosquito-control officials have said that while Sacramento County became the epicenter of West Nile in 2005, the spike in cases traditionally found when the virus sweeps into an area failed to show up in Yolo County.

That warning is consistent with a study by the UCD researchers.

Walter Boyce, a veterinarian and expert in wildlife health, said that from October 2004 through November seven of 55 American crows monitored with radio transmitters died. Of those, just two were found to have died by the virus.

Elsewhere in the country, two-thirds to three-quarters of crows have died in places when the virus first hit.

In August, the researchers devised a way to use the transmitters on the smaller magpies. Since then, three of 20 birds tracked have died, one of them from West Nile.

"The data suggest that this coming year will be another big year here," Boyce said. "I like to think of West Nile as like a wildfire that leaves patches unburned. This year, northern Sacramento County was a hot spot. There's a lot of fuel here (in Davis)."

Ernest said Thursday's meeting will yield a group letter to state agencies, a list of priorities for monitoring yellow-bills and, most likely, a new working group to study them.

Public concern

Another priority should be shining a spotlight on the risk to the species, she said: Public concern can help attract both the attention of government agencies and private organizations and funding for research.

Ernest said the public can also play an important role in research (see box).

Though specific solutions to the problem weren't discussed formally at the meeting, those who attended did offer some possibilities.

They included increasing mosquito-control measures in areas where yellow-bills congregate to, in a dire situation, capturing birds and placing them in a breeding program.

Legal tools might also be used to protect the birds' dwindling habitat, though such efforts usually make for slow-going.

Yellow-bills are not listed as a protected species at the state or federal level. And Steele said that they will probably not be added to a new state list of species of special concern, due out next year, because the work on it was done before West Nile took hold.

A new law requiring counties to plan for the conservation of oak woodlands, where magpies often live, may offer ways to help protect the birds, he said.

Crosbie thought often about the looming specter of West Nile as he did his magpie research. He said he has reason to be hopeful for the birds he grew up watching in Sacramento, thanks to Thursday's meeting.

"Maybe it could have happened sooner," he said, "but that doesn't make it any less important."